import java.util.Scanner;

public class demo13 {
    public static int minCostClimbingStairs(int[] cost){
        int n = cost.length;
        int[] dp = new int[n+1];
        for (int i = 2; i <= n ; i++) {
            dp[i] =Math.min(dp[i-1] +cost[i-1],dp[i-2]+cost[i-2]);
        }
        return dp[n];
    }
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int size = in.nextInt();
        int[] arr = new int[size];
        for (int i = 0; i < size; i++) {
            arr[i] = in.nextInt();
        }
        System.out.println(minCostClimbingStairs(arr));

    }






}